It is known in the art to lock a nut in a screw and nut joint, e.g., by using another nut which is tightened against the nut to be locked, or by using a nut made in two parts each with a threaded portion and being rotatable in relation to each other. Such locking devices generally consist of a plurality of loose parts and are, therefore, complicated to handle. Further, a locking nut or nut part has to be tightened forcefully against the nut or nut part which constitutes the active part of the screw and nut joint, which makes it difficult to determine the exact position of the last mentioned element on the thread, or the pre-stress of the screw and nut joint, because the locking nut or nut part acts with a torque on the other nut or nut part when it is being tightened, causing said other nut or nut part to be turned so that its position on the thread or its pre-stressing force against a supporting surface is changed during the locking operation.
It is also known to make a nut lockable by providing it with a slot in a plane perpendicular to the thread and through a portion of it and varying the width of the slot, thereby causing a clamping action in a portion of the nut thread by means of an axially arranged screw which extends through the slot. Such a nut has to be comparatively thick in order to provide a space for the slot, and making such a slot in the nut is expensive and complicated.